The present invention relates to bearing inserts for operably supporting a rotatable shaft, such as a camshaft in an internal combustion engine, and further relates to a method for repairing spaced-apart bearing supports to receive the bearing inserts, and still further relates to a broaching tool for use in the method.
Modem internal combustion engines for passenger vehicles typically include a cylinder head and a camshaft rotatably supported at journals by the cylinder head at multiple aligned bearing locations. The cylinder heads include a bearing support structure (sometimes called xe2x80x9cbearing housingsxe2x80x9d) at each of the bearing locations. An oil port is included in each bearing support structure for passing oil to journals on the camshaft. As engines age, the bearing surfaces on the cylinder head and the journals on the camshaft wear, such that these bearing locations sometimes need to be rebuilt. In extreme cases, galling and material deformation may occur, causing the camshaft to roughly rotate or even freeze up on the cylinder head. It is known to repair these bearing locations by welding on the cylinder head to reapply material to the support structure, and thereafter to machine away excess material to reform the bearing surfaces. It is also known to simply machine away material on the cylinder head to form an oversize bearing surface. A problem is that accurate alignment of the bearing locations along a camshaft is very important so that the camshaft is properly positioned for rotation without stress, and so that the intake and exhaust valves of the internal combustion engine work properly, set up for good alignment to re-cut the bearing locations is expensive and time consuming and can easily be done wrong. Further, the tools for cutting and machining the bearing locations can be expensive. Also, a plurality of different tools is required for each different bearing size, such that it requires significant capital investment for a repair shop. There are also the frustrations of not having (or not being able to find) the right size cutting tool for a particular size bearing.
It is known to cut away the bearing support structure and to locate a whole new massive outer bearing in the structure head to support the camshaft. Further, it is known to purchase new replacement camshafts having particular sized camshaft bearing surfaces. However, it is undesirable to cut away substantial material from the cylinder head of modern engines since this can affect their strength, operation, and heat flow in the cylinder head in adverse ways. Further, removal of large amounts of material can lead to mistakes that totally destroy cylinder heads.
Notably, broaching apparatuses and methods have been used to machine internal combustion engine components for many years. For example, see U.S. Pat. Nos. 5,224,804 and 5,435,676. U.S. Pat. No. 5,435,676 discloses a two-stage broaching method wherein the first broach is advanced through the bores, leaving unbroached ridges therebetween. A second broach then broaches the ridges that are left by the first broach. U.S. Pat. No. 5,224,804 discloses a tooling system and method for broaching engine components wherein the broach bar is forwardly passed through the engine block with the bearing bores being opened a progressively to their final diameter. Thus, there is a need for a one-stage broaching apparatus and method wherein the broach is pulled through the cam housings while accurately and ad efficiently machining the cam""s bearing surface.
Accordingly, there is a need for a reliable bearing insert and a related method and tools that solve the aforementioned problems and that have the aforementioned advantages.
In one aspect, the present invention includes a broaching apparatus for use in a structural body having spaced-apart bearing supports with aligned holes defining an axis. The broaching apparatus includes an elongated broach having a longitudinally extending hole extending from end to end of the broach and having first threads formed along at least a portion of the longitudinally extending hole. The broach has a lead section, a cutting section, and a tail section. The cutting section is configured to enlarge the aligned holes from a smaller first diameter to a larger second diameter, and the lead and tail sections are configured to guide the broaching tool linearly through the aligned holes while maintaining accurate alignment with the aligned holes. The broaching apparatus further includes a motivating device including a broach puller and a holder rotatably receiving the broach puller. The broach puller has a shaft that extends through the holder with second threads on one end configured to mateably engage the first threads. The broach puller further has a configured end opposite the one end that is shaped to be engaged and rotatably driven by a machine or hand tool, such as an air impact wrench. The holder includes a first end section rotatably abutting the configured end of the broach puller and a second end section configured to abut the structural body. Thus, the aligned holes in the structural body can be broached by pulling the elongated broach through the aligned holes by rotating the broach puller.
In another aspect, the present invention includes a method of repair comprising steps of providing a cylinder head for an internal combustion engine having spaced-apart bearing housings configured to rotatably support a camshaft, one of the camshaft bearing housings having a galled, non-uniform bearing surface in need of repair; enlarging the non-uniform bearing surface to a slightly oversized condition to form an enlarged bearing housing and positioning a thin-walled insert on the camshaft and in the enlarged bearing housing and frictionally retaining the thin-walled insert in place in the enlarged bearing housing and rotatably supporting the camshaft in the thin-walled insert.
In another aspect, the present invention includes a method of repair comprising steps of providing a cylinder head having spaced-apart and aligned bearing housings configured to rotatably support a camshaft with at least one of the camshaft bearings being galled and in need of repair. The method further includes providing a broach configured to be pulled linearly through the aligned bearing housings to enlarge a diameter of the shaft bearing housing and broaching the galled camshaft bearing by pulling the broach linearly through the galled bearing housing. The method also includes applying polymeric compound to the galled camshaft bearing to fill in void areas.
In yet another aspect, the present invention includes a method of repair comprising steps of providing a cylinder head having spaced-apart and aligned bearing housings configured to rotatably support a camshaft, the camshaft bearings being in need of repair, and providing a broach configured to be pulled linearly through the aligned bearing housings to enlarge a diameter of the camshaft bearing housings. The method further includes broaching at least one of the camshaft bearing housings to an oversized diameter by pulling the broach linearly through at least one bearing housing and positioning at least one insert on the camshaft and in the at least one bearing housing with the camshaft being rotatably supported in the insert.
These and other features, advantages and objects of the present invention will be further understood and appreciated by those skilled in the art by reference to the following specification, claims and appended drawings.